An alternative that is basically free is the IGCdroid app, sending the track data to glideport.aero. But it has to run on people's cellphones, and they have to turn it on, so it's not reliably attached to the gliders. And it requires an Android phone. There is a similar iOS app although it's less flexible. Also this method requires at least occasional cellphone data access from the glider. Around here the coverage seems good enough.